The present invention relates to fiberoptic illumination systems and more particularly to fiberoptic illumination systems used in ophthalmic surgery.
Fiberoptic illumination systems are widely used in the medical field for illuminating body cavities, particularly during endoscopic (small incision) surgery. These devices generally include some means for attenuating the luminous density or light-flux of the light beam.
For example, the luminous density or light-flux from the light source can be controlled by varying the feeding current or voltage to the light source. This method of attenuating the light source will change the color temperature of the light and thus the color of the object illuminated. Various attenuating filters may also be used, but attenuating filters can reduce maximum illumination of the cavity. Optical diaphragms such as an iris diaphragm will change the entrance and exit angles of the light beam into and out of the optic fiber. Sectored or fan-fading diaphragms, such as those disclosed in U.S. Pat. No. 4,233,650, reduce the maximum illumination of the cavity. Wedge-shaped shutters, such as those disclosed in U.S. Pat. Nos. 3,106,800 and 4,425,599, do not substantially reduce the maximum amount of illumination in the cavity; however, these types of shutters preferentially attenuate the outer ("cooler") portion of the light beam, and do not commensurably attenuate the inner ("hotter") part of the beam, thus resulting in a hotter light beam (change in color temperature) exiting the fiberoptic. In addition, attenuating only the outer portion of the beam results in non-optimal illumination of the numerical aperture of the fiber and poorer light mixing in the fiber.
One prior art device sold by Grieshaber & Company, Inc., includes an ultraviolet (UV) filter; however, the UV spectrum of the lamps used in this and other illumination systems generally is considered to extend from 200 nanometers (nm) to 400 nm, and wavelengths longer than 400 nm have been shown to be injurious to the retina.
Accordingly, a need continues to exist for a fiberoptic illumination system that allows for the uniform attenuation of the amount of light reaching the fiberoptic without changing the color temperature or entrance angle of the light or reducing the maximum amount of light reaching the object to be illuminated. A need also continues to exist for a fiberoptic illumination system that attenuates the wavelengths of light shown to be injurious to the retina.